Cathodoluminescence device for scanning electron microscopes

ABSTRACT

A cathodoluminescence device for scanning electron microscopes which comprises a hollow space for arranging a specimen therein, and said hollow space having at least one focus and provided with a reflecting cover.

United States Patent 1191 Horl et al. Feb. 5, 1974 [54]CATHODOLUMINESCENCE DEVICE FOR SCANNING ELECTRON MICROSCOPES [56]References Cited [75] Inventors: Erwin Horl; Peter Scholze; EduardUNITED STATES PATENTS Mugschl 3110f Ausma 3,319,071 5/1967 Werth 250/435R [73] Assignee: Oesterreichische Studiengesellscha ft fur AtomenergieGesellschaft Primary Examiner-James W. Lawrence m.b.H., Vienna, AustriaAssistant Examiner-C. E. Church [22] Filed: Sept 28, 1972 Attorney,Agent, or Firm-Ernest G. Montague [21] Appl. No.: 292,954 v [57]ABSTRACT A cathodoluminescence device for scanning electron [30] Fore'gnApphcauon Pnomy Dam microscopes which comprises a hollow space for ar-OCL 5, 1971 Austria 8603/71 ranging a specimen therein and aid hollowpace having at least one focus and provided with a reflect- 52 US. Cl.250/310, 250/491 mg Coven [51] Int. Cl. H01j 37/26 58 Field of Search250/495 B, 49.5 PE 6 Claims, 1 Drawing Figure CATHODOLUMINESCENCE DEVICEFOR SCANNING ELECTRON MICROSCOPES The invention refers to acathodoluminescence device for scanning electron microscopes.

Using the known cathodoluminescence devices for scanning electronmicroscopes either light conductors the front faces of which survey justvery small solid angles are brought near to the specimen or the lightproduced at the specimen is focussed by an optical lens onto the frontface of a light conductor or directly onto a detector. Even in thesecond case the solid angle surveyed is small compared to the solidangle of the apparatus described below, and thus the sensibility gainedby such devices is low. Further it is not possible with the devicesknown at present, to prevent energised electrons back-scattered at thespecimen from hitting the front face of the light conductor or the lens.By this hitting scintillations are produced which give rise to a noiseor interfering signal. In case that the specimen just shows a very lowcathodoluminescence it is often not possible anymore on account of thisnoise signal to use the cathodoluminescence for the representation ofthe specimen by the scanning electron microscope.

In accordance with the invention it is proposed now that the specimen isplaced into a hollow space coated with a reflecting layer and having atleast one focus. By this provision the disadvantages mentioned above areavoided.

The invention will now be described further by way of the drawings.

The inventive device comprises a block 3 having a bore 2. Within theblock 3 there is a hollow space 5. The most advantageous geometricalconfiguration for this hollow space 5 has been proved to be thesemiellipsoid of revolution. However, the hollow space might also be ahemisphere. The curved face of the hollow space is provided as a mirror4. Into this hollow space 5 the specimen 6 is placed at theone focus 7of the ellipsoid and is arranged below the bore 2 through which theelectron ray 1 passes. The light produced at the surface of the specimenis focussed by the mirror 4 at the other focus 9. At this focus ashutter 8 is provided the centre of aperture of which coincides with thefocus 9. By means of the light conductor 10 being made preferably fromquartz, the light passing the shutter aperture is guided to a detector111. In front of this detector an optical filter 12 is arranged whichpreferably prevents the passage of this spectral range comprising thewave lengths of the light quanta being released by the fast electrons atthe entrance face of the light conductor 10; thereby a decrease of thenoise signal in the detector 1 1 is achieved. In the radiation path ofthe primary electron ray 1 a thin aluminium foil is arranged to cut outthe incandescent light of the electron gun.

The block 3, the specimen 6 and the light conductor 10 together with theshutter 8 are arranged on a support 13 being attached to the specimenmotion tongue, not shown, of the scanning electron microscope. By thefact that the shutter 8 is arranged in front of the light conductor 10the number of the highly energized electrons hitting the light conductoris strongly reduced.

However the light quanta focussed in the focus 9 are not affected. Theblock 3 and the mirror 4 consist of a material having a low atomicnumber thus a further back-scattering of the highly energized electronsbeing already reflected at the specimen is lessened.

The invention is not restricted to the shown examples. The hollow spacemight also be a hemisphere, then the specimen is arranged eccentrically.Moreover it is not absolutely necessary that the complete inner face ofthe hollow space is covered with a reflecting layer. In parallel to thebottom of the hollow space a bore might be provided through which thesecondary electrons might be drawn off. These secondary electrons can beused for generating a representation.

We claim:

1. An electron-microscope cathodoluminescence device, comprising asupport having a face,

a block disposed on said face of said support and forming a hollow spacehaving a semi-ellipsoidal surface of revolution and having two foci onsaid face,

means for positioning a specimen at one of said foci, a light reflectinglayer at least partially coating said semi-ellipsoidal surface,

said block being formed with a bore,

electron ray means for passing an electron ray through said bore ontosaid specimen, and

a detector means for detecting light emitted by said specimen disposedat the other of said foci.

2. The device, as set forth in claim 1, wherein said detector meanscomprises,

a light conductor having an end disposed at said other of said foci, and

a detector in communication with another end of said light conductor.

3. The device, as set forth in claim 1, further comprisa shutter havingan aperture, the latter disposed coinciding with said other of saidfoci.

4. The device, as set forth in claim 1, wherein said reflecting layerand block comprise a material having a low atomic number.

5. The device, as set forth in claim 1, further comprisa thin aluminumfoil disposed in the radiation path of said electron ray.

6. An electron-microscope cathodoluminescence device, comprising asupport having a face,

a block disposed on said face of said support and forming a hollow spacehaving a hemispherical surface and having one focus on said face,

means for arranging a specimen eccentric to said focus, a lightreflecting layer at least partially coating said hemispherical surface,

said block being formed with a bore,

electron ray means for passing an electron ray through said bore ontosaid specimen,

a detector means for detecting light emitted by said specimen positionedat said focus.

1. An electron-microscope cathodoluminescence device, comprising asupport having a face, a block disposed on said face of said support andforming a hollow space having a semi-ellipsoidal surface of revolutionand having two foci on said face, means for positioning a specimen atone of said foci, a light reflecting layer at least partially coatingsaid semiellipsoidal surface, said block being formed with a bore,electron ray means for passing an electron ray through said bore ontosaid specimen, and a detector means for detecting light emitted by saidspecimen disposed at the other of said foci.
 2. The device, as set forthin claim 1, wherein said detector means comprises, a light conductorhaving an end disposed at said other of said foci, and a detector incommunication with another end of said light conductor.
 3. The device,as set forth in claim 1, further comprising a shutter having anaperture, the latter disposed coinciding with said other of said foci.4. The device, as set forth in claim 1, wherein said reflecting layerand block comprise a material having a low atomic number.
 5. The device,as set forth in claim 1, further comprising a thin aluminum foildisposed in the radiation path of said electron ray.
 6. Anelectron-microscope cathodoluminescence device, comprising a supporthaving a face, a block disposed on said face of said support and forminga hollow space having a hemispherical surface and having one focus onsaid face, means for arranging a specimen eccentric to said focus, alight reflecting layer at least partially coating said hemisphericalsurface, said block being formed with a bore, electron ray means forpassing an electron ray through said bore onto said specimen, a detectormeans for detecting light emitted by said specimen positioned at saidfocus.